I'm sure these buildings had bricks--but the most important architectural feature of Roman engineering was their discovery and use of concrete. The concrete process was lost for hundreds of years during the Dark Ages, but it was the strength and malleability of concrete that made the great acqueducts and buildings with domes possible.
The secret to Roman concrete was the use of volcanic material, and when they set the concrete into place, they used special tools to pound the excess water out of the concrete.
The Romans didn't use bricks so much as a structural material as a decorative facade..
Concrete made up the "bones" and the outside face was "prettied up" with fancy brickwork, often stamped or pressed with designs to make them look even better..
You're right about the concrete..
Cement was first used by the Assyrians, and the Egyptians were familiar with it as well..
The Etruscans used "additive" in their cement, so it might qualify as a sort of concrete, but concrete is defined by the use of "aggregate", i.e., the crushed rock, small stone and gravel added to the cement..
And that is, truly a roman "invention" or discovery, depending on how you look at it..
Something else the Romans did not many know about..
They learned that concrete / cement could be made "stickier" with the addition of gluten..
In the case of the Romans, they used, for the most part, wheat, boiled down into a thick sticky liquid.. This was then added to the concrete (or cement) mix to insure superior adhesion..
The Chinese, I believe, did the same thing, using another, similar ingredient.. Rice..
Again, boiled down to make rice glue, then added to the cement / concrete..